Place the tomatoes, yellow pepper, black beans, red onion, jalapeno peppers, and lime zest in a large bowl. Whisk together the lime juice, olive oil, salt, black pepper, garlic, and cayenne pepper and pour over the vegetables. Toss well. This mixture can be refrigerated for 3-4 hours before serving.

Just before you're ready to serve the salad, fold the avocados into the salad. Check the seasoning, adding salt and pepper to taste if needed, and serve at room temperature.